Previously, a crosslinked sodium polyacrylate salt has been used as a water-absorbing resin in a variety of utilities. However, in this composition, an amount of absorbing water or urine is high, but a resin is not swollen at all in an organic solvent. Therefore, the resin is not applied as an agent for absorbing an organic solvent or as a gelating agent.
As a crosslinked resin which absorbs an organic solvent, for example, there are proposed:
(1) a crosslinked polymer of a monomer containing a tertiary or quaternary amino group such as dialkylaminoalkyl(meth)acrylate, (meth)acryloyltrialkylammonium chloride and the like (JP-A No. 58-154709 gazette),
(2) an alcohol absorbent comprising a crosslinked copolymer of the aforementioned tertiary amino group-containing monomer and a vinyl monomer having a carboxyl group (JP-A No. 60-179410 gazette, JP-A No. 60-192717 gazette etc.),
(3) an oil absorbent comprising crosslinked (meth)acrylate of a monovalent aliphatic alcohol having a carbon number of 10 to 16 or a crosslinked monomer having a solubility parameter of 9 or smaller (JP-A No. 3-221582 gazette, JP-No. 4-100539 gazette etc.),
(4) a liquid-absorbing resin comprising crosslinked alkoxyalkyl (meth)acrylate and the like or crosslinked N-vinyllactam (JP-A No. 10-101745 gazette, JP-A No. 11-35632 gazette etc.),
(5) a liquid-absorbing resin comprising crosslinked N-vinylacetamide (JP-A No. 4-230250 gazette, JP-A No. 8-59743 gazette).
In addition, in the fields of lithium batteries and condensers, a polar organic solvent such as propylene carbonate and γ-butyrolactone is usually used as an electrolyte solution. In order to make a battery thin or to prevent solution leakage at damage, there is a great demand for gelating this organic solvent. As a polymer for gelating an electrolyte solution, for example, there are proposed:
(6) crosslinked polyalkylene oxide (hereinafter, referred to as PEO system, JP-A No. 62-285954 gazette, JP-A No. 6-68906 gazette and many publications),
(7) crosslinked polyacrylnitrile (hereinafter, referred to as PAN system, JP-A No. 8-264205 gazette, JP-A No. 2000-58078 gazette, JP-A No. 2000-223105 gazette etc.),
(8) crosslinked polyacrylic acid ester, and
a method of using a polymer having the same composition as that of the (1) as a gelating agent for an electrolyte solution (JP-A No. 2000-331533 gazette, 2001-123073 gazette etc.).
However, although the crosslinked polymer of (1) exhibits a relatively high amount of absorbing an alcohol, the polymer has a low amount of absorbing an organic solvent other than an alcohol, for example, propylene carbonate, γ-butyrolactone, toluene and the like, and at the same time, an ester group of this kind of cationic polymer is extremely easily degraded at a region of a pH 4 or larger due to intramolecular interaction between an amino group and an ester group, and therefore, there is a problem that the polymer is not suitable for utilities requiring durability of a polymer, such as a gelating agent for an electrolyte solution.
In addition, regarding crosslinked polymers of (3) to (8), since these polymers are fundamentally a nonionic polymer, dissociation of a polymer does not occur in the aforementioned subject organic solvents. Therefore, those polymers have weak capabilities of absorbing and gelating subject organic solvents and, in order to absorb and gelate these organic solvents, it becomes necessary to add a large amount of a polymer. There is a problem that not only this is uneconomical, but also when used in utilities such as batteries and condensers, addition of a large amount of a polymer reduces an electrical conductivity of an electrolyte solution, and deteriorates electrical properties.
Further, lithium batteries and condensers are used in mobile phones, computers, various appliance products and the like. However, there is a problem that, when an organic solvent-based electrolyte solution is leaked, a harmful gas is generated, substrates of other ICs and semiconductors are polluted, and ignition occurs in some cases. Regarding prevention of leakage of these electrolyte solutions, only a non-woven fabric sheet is practically proposed. The non-woven fabric has an extremely small solution holding amount to these electrolyte solutions. When there is a great leakage, this can not be defended at all. Therefore, there is a great demand for development of a sheet which can hold a large amount of these organic solvents.
In view of the aforementioned circumstances, the present inventors intensively studied, and as a result, found that a non-aqueous absorbent comprising a crosslinked body having a particular composition has extremely high capabilities of absorbing and gelating the aforementioned organic solvents, a large amount of organic solvents can be absorbed and gelated by addition of a small amount of the non-aqueous absorbent, and a sheet containing the non-aqueous absorbent has an extremely high amount of holding the aforementioned organic solvents, and can hold a large amount of those organic solvents, which resulted in completion of the present invention.
An object of the present invention is to provide a non-aqueous absorbent which has extremely high capabilities of absorbing and gelating organic solvents, and can absorb a large amount of organic solvent and gelate organic solvents by addition of a small amount of the same.
Another object of the present invention is to provide various uses of this non-aqueous absorbent in various forms.